1-Cyclopropyl-6,7,8-trifluoro-1,4-oxo-3-quinoline carboxylic acid is a key intermediate in the preparation of 7-aminosubstituted-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-3-quinolin ecarboxylic acids described in German Offenlegungschrift No. 3,318,145 and U.S. patent application Ser. No. 692,820. These 7-aminosubstituted-1-cyclopropyl-6,8-difluoro-4-oxo-quinolines are useful as antibacterial agents.
1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid may be, in turn, prepared by a series of steps starting with 2,3,4,5-tetrafluorobenzoic acid.
2,3,4,5-Tetrafluorobenzoic acid is not commercially available since it is difficult to synthesize. G. C. Yakobson, et al., in Zhurnal Obshchei Khimii, 36 (1), pgs 139-42 (1966), describe such synthesis by the decarboxylation of tetrafluorophthalic acid at 145.degree. C. The present invention relates to a new process for 2,3,4,5-tetrafluorobenzoic acid which provides a 25-30% yield improvement over the previously described method.